Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
H,W=map(int,input().split())
s=[['#']*(W+2)for _ in range(H+2)]
count=0
for i in range(1,H+1):
  S=list(input())
  s[i]=['#']+S+['#']
  count+=S.count('.')
move=[(1,0),(-1,0),(0,1),(0,-1)]
que=deque([(1,1)])
s[1][1]=1
while que:
  a,b=que.popleft()
  if (a,b)==(H,W):
    break
  for my,mx in move:
    ny=my+a
    nx=mx+b
    if s[ny][nx]=='#':
      continue
    elif s[ny][nx]=='.':
      que.append((ny,nx))
      s[ny][nx]=s[a][b]+1
ans=-1
if s[H][W]!='.':
  ans=count-s[H][W]
print(ans)